[This post on spirits acidity was written about five years ago and some how generated a huge amount of google search returns. In the time since, my understanding of the matter has gotten a huge upgrade, but there is still a lot of questions.]
A fairly accessible and historically significant paper on the topic is Studies with Brandy. I. pH by Guymon, Tolbert, and Amerine who were giants in beverage technology. These papers were planned as a series but due to the “exigencies of war” (WWII) only the paper on pH and another on tannin from barrel aging were published. Strangely, these two papers do not appear in any bibliographies that I can remember.
I’ll try and pull some unique things out of the paper and I’ll leave everything I’ve written previously in tact below.
“The pH of seven whiskies varied from 3.68 to 4.78, the highest value being a new whisky.” I think the pH of even the new whisky here is lower than some would think due to a significant amount of volatile fatty acids.
“In rum Valaer (1937) found the pH to vary according to the source, exceeding 5 for Cuban and Puerto Rican rums. The pH of rums distilled in this country was lower.” The pre-Castro cuban rums referenced here have a higher pH because they were relatively more neutral and closer to a vodka. So when we look at these old papers I suspect the pH of new make spirits can say a lot about congener profile.
“The low pH values of young brandies were attributed to the use of distilling material higher in sulphur dioxide. A portion of the sulfur dioxide passing through the still is dissolved in the distillate and is slowly oxidized from sulphurous acid to sulphuric acid. Presumably this is not always the cause of low pH in brandies, for 20 authentic French cognacs, in which the sulfate content owing to oxidation of sulfite is relatively low, the pH was found to vary from 3.76 to 4.98, averaging 4.14.” What they are getting at here is that back in the day a lot of wines intended to be table wines went through the still and because table wines get added sulphur they ended up with a confusingly low pH even though they were probably well rectified and deficient in fatty acids. When a wine is constructed specifically for distillation sulphites are never added.
“pH’s as low as 2.24 and as high as 7.97 were found in certain anomalous samples reported by Valaer in a private communication giving in detail the original data.” This foot note is historically very interesting. Peter Valaer was the great IRS chemist who probably saw and deconstructed more spirits of more types than any ever in the history of beverage science. The foot note shows that the UC Davis guys new Valaer personally beyond just his papers.
“It is therefore evident that the pH of commercial distilled spirits ranges from 4 to 5, that it tends to decrease during ageing, and it appears that rum has a higher average pH than the other distilled spirits.” I think the rums they refer to here are the fairly neutral “dry” rums.
“Some of these abnormally high pH’s are probably due to the distillation of neutralized distilling material and the consequent lack of volatile acids in the distillate.” Neutralizing distilling material with baking soda is practiced by home distillers making spirits from Turbo Yeasts. Often their fermentations get “pricked” and excess acetic acids needs to be neutralized before distillation but at the risk of converting an ammonium salt into volatile ammonia which can corrode the condensor producing a distillate tinged with blue verdigis.
“The buffer capacity of new alcoholic distillates is so low that the addition of only small quantities of either acid or alkaline substances results in abnormally high or low initial pH; for example the use of alkaline water for cutting may result in high pH. Caramel syrups are not stable in alkaline solutions and the brandies with a high pH precipitated most of their caramel as a gummy, reddish mass.” This reference to buffer capacity might be why UV vodka referenced in the original post is proud of their pH neutrality. Cheap vodka might have a lower pH because un-desired fatty acids remain in their distillates. When an old fashioned is batched (guilty!), the sugar probably does not precipitate because the pH is far lower than the fairly pH neutral spirit they are referencing which is basically the brandy equivalent of grape drink.
“Newly distilled brandies with a pH below 4 are also abnormal. Valaer (1939) found a number of the young California brandies of very low pH and, as already mentioned, he explained this on the basis of their high sulfurous-sulfuric acid content.” California used to make sloppy shit! but if you look back at the early days of wine as described by Allan Hickenbothan at Roseworthy in Australia, back in the 1920’s they had a 30% failure rate on wines meant to be table wines and they were all sent to the still. After Hickenbothan discovered the significance of pH and started acidifying wines, what they sent to the still decreased to 5%.
*****
Lately I see the word dry confusingly placed on all sorts of spirits from gin to rum and I don’t really understand what it means. dry is even confusingly used in wine speak. Many people can’t make heads or tales of whether a wine is sweet or not. Is there unfermented sugars or are people referring to levels of acidity? many people think rums are sweet because they are made from sugar but that sugar is transformed into alcohol as well as not-volatile so if rum has sugar it is added post distillation. Well whats the deal?
If like wine, dryness often ends up referring to acidity, what is the acidity of spirits? Should un-aged spirits mostly be the same and there be some difference in aged spirits? is there perceived sweetness due to high extracts in spirits like some times is encountered in wine?
The UV vodka website proudly claims their product is close to pH neutral relative to other budget producers who acidify their product for some spirits tax loophole. This makes really no sense to me but the budget producers would definitely have some dry booze. Could these practices in neutral spirits be born out of some sort of tradition? Should my C.J. Wray dry rum be fairly low in pH? and if it is, would the result be due to additives or stuff naturally going through the still?
Maybe to solve some of the mystery I should calibrate my Hanna Instruments pH pen and have a go at the spirits that are laying around.
Calibrated with fresh solution.
Whole foods distilled water. pH??? Well my distilled water was below 7 which is kind of a bad omen, but maybe acid is attached to my electrode from my cleaning solutions etc? Maybe the temperature is messing with things? Well I put on a new electrode, calibrated it and I still can’t get a 7 out of this distilled water but maybe its is messed up.
C.J. Wray dry rum pH 4.85
Gordon’s dry gin pH 6.90 <— switching back and forth and this rockets back to 6.90 so the pen works?
Myer’s platinum white pH 4.42
Clement VSOP pH 3.78
Back to the calibrators… things check out… more or less… I tried to go back and forth between samples to duplicate my initial numbers. More or less they check out.
Batavia Arrack Van Oosten pH 5.02
Seagram’s Distiller’s Reserve pH 5.13
Trimbach Framboise raspberry brandy pH 6.80
lemon juice pH 2.37 (time for a cocktail!)
So wow, I don’t really have too much confidence in the tester but I think it can still teach something about what we drink. It is strange how drastically different Gordon’s and the Trimbach are from the others. Your choice here would apparently have a large impact on balancing a sour. Are the results here the reason the rum & coke is more popular than the fairly acid neutral UV with coke? Harold Mcgee puts black coffee at pH 5.0 and yogurt at pH 4.5. So are the results here negligible because we pile on the sugar with our mixers or are these pH factors important in shaping consumer preference over the long run?
Now I’m curious how the more mainstream gins that I work with at the bar stack up, and how does all this acidity get there in the first place? any insights?
I haven’t really put things to test on what comes through my still, but now I’m even more curious and I think I’m going to have to test some things… distilled, citric, malic, tartaric, and acetic acids… and it was the last of my bottle, but if I added baking soda to the low pH Clement would it have fizzed? could I neutralize that acidity?
Do some dry gins have more acidity now because the palate needs it in a martini (or maybe not, it is my assumption from loving dry wine) but no one wants to get it from dry vermouth. So does a great marriage of gin and dry vermouth like you see in weird reviews really have to do with finding a most harmonic pH?
Quite a lot of new mixology questions.
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Wow, interesting, but I don’t know what conclusions to draw.
I did some googling and pure ethanol should give a ph reading of around 7.9 or slightly basic.
When cuts are made during distillation, ph of water used to dilute, and additives…
I would imagine the chemicals which the alcohol aged in oak releases from the barrels would also affect ph.
i think wood has a big effect on PH and i think its in one of amerine’s books somewhere… i will look. i wonder what the array of spirits additives are? its known that vodka producers round out their flavors with oils and weird stuff but acids don’t really make things smoother… so citric acid in your gin? i think i’m going to investigate the distilling msg boards…
Well, additives vary with the rules for the particular spirit.
Nothing other than water is allowed for any of the American Straight Whiskies.
Rum, however, is given a huge latitude, as are blended spirits. Up to the distiller/manufacturer.
Not sure what the rules are for gin. I remember Eric Seed said he was pretty surprised when he started doing sugar content testing on the big gins.
i wonder how he did his tests. i have up on the refractometer because i found out that alcohol in the solution really obscures its readings. you could test easily by using a proof hydrometer and see how if it read what was printed on the bottle’s label. minimal sugar changes the readings significantly. its hard to find a proof hydrometer that would give finer readings in that range. i have one that does fine readings but only from the 20% to 40% range.
http://www.ginvodka.org/factsheets/london.asp
“g. A small amount of sweetening may be added after distillation provided the sugars do not exceed 0.5 grams/litre of finished product (the sugar is not discernible and is added to some products purely for brand protection purposes). ”
“h. The only other substance that may be added is water.”
so maybe we should expect these london gins to be acid neutral? or is there a loop hole in the water they are allowed to add?
supposedly the sugar is not to be discernible but for “brand protection” maybe to obscure examining the density the oil contribute?
the site also explains that the meaning of the “dry” in “london dry” was to distinguish from the sweetened “old tom” style.
With regard to the distilled water, this isn’t a reason to doubt your tester. The carbon dioxide from the air dissolves in water making carbonic acid so the pH will be less then 7 – probably around 4.2. Also it is notoriously difficult to get a stable pH measurement on distilled water because there aren’t enough solutes to get a good potential at the electrode surface.
It would be interesting to see the pH of your mixed drinks. From your results, I would expect most to be on the acidic side – even ones that aren’t sours.
where have you been all my life? now we are finally getting somewhere… (hard to get comments around here) do you think i can trust my other readings? i would really love to analyze vermouths, and some liqueurs like st. germain, sloe gin, etc… and what i really want to investigate is how changes in gin production over the vast years could change the mysterious dry martini…
A couple things..
I always thought dryness referred to the perceived sweetness of a drink rather than its acidity per se. Perceived sweetness can vary based on acidity, alcohol content, tannins, other organic carbohydrates etc. Such that acidity alone is not necessarily a good indicator. All in all, my feeling is that dryness is a sensation that involves a lot of different factors.
As for the technical issue of measuring pH. Did you calibrate your pH meter with 2 buffers? Usually I calibrate with pH 4, 7, and 10 when needing to use a pH meter (making solutions in a research lab). As the other commenter mentioned, distilled water is not usually neutral due to CO2 (but I don’t think its 4.2 either.. That would put it around the same pH as acid rain. As a point of comparison, “normal” rain has a pH of around 5.6, which is probably the lowest pH you will see for distilled water due to atmospheric CO2). However, my guess is that any acidification due to distillation would occur also acidify any alcohol distillate, since its mostly the process of condensing vapor that leads to inclusion of CO2. Moreover, I would think that the CO2 levels in a still would be higher than atmospheric levels due to production of CO2 as a byproduct of ethanol fermentation. Other contributing factors to acidity may include the pH of the water used in the manufacturing process, aging process, etc. Also, I’d be curious to know the effect that the ethanol-water binary solvent has on solubility of aromatic organics… Wow, I feel like I’m back in Orgo again..
By the way, really enjoy your blog! I’ll be moving to Boston next year, and its exciting to know there’s such a great mixology community there!
an astounding amount of people search google to see what the PH of gin is and if it has acidity. here is a little snippet from a 19th century book that covers the adulteration of gin.
“mostly With regard to spirits gin is adulterated with acid and sugar and this is very easily detected by nitrate baryta which gives rise to an insoluble white when it is added to a solution of sulphuric acid Not is gin adulterated with sulphuric acid but vinegar is adulterated with the same agent It is added to gin it tends to give the gin a greater amount of pungency and that state it admits of a large amount of dilution for there scarcely any of the gin which is sold retail at the houses which does not contain a certain quantity of acid and sugar and the quantity of alcohol is reduced very much below the amount contained in the gin as supplied by the distillers I will say however with regard those gins which the distillers call family gins or gins that they consider themselves privileged to add a certain quantity of sugar ”
Water without solutes should be below pH 7. RO water for instance often comes in at 5 or less. I believe the comment above addressed the CO2/carbonic acid thing. Another item to keep in mind about this is that in distilleries RO water is used to dilute spirit and there is an abundance of CO2 about due to fermentation. Great articles sir!
Professional Sommelier & Beverage Director here, confirming that ‘dry’ (misleadingly, I know) refers to a lack of sugar in wine, not perceived ‘drying’ of the palate caused by acidity or tannins.
Great to hear from you William,
Wow, that post was long ago. I’d say that dry is more complex a term than lack of sugar. There is relative dryness even for wines fermented to “dryness” which encompasses both acidity and nature of the aroma. A convention I’ve started using when categorizing olfaction in terms of gustation is to hyphenate such as olfactory-acidity or olfactory-sweetness. You may enjoy the writings elsewhere on the blog about synaesthesia versus non-linguistic contrast detection.